The iPhone Dev-Team has confirmed that RedSn0w 0.9.6b2 can jailbreak iOS 4.2 GM Seed; however, they warn it should only be attempted by advanced users.

This tutorial will show you everything you need to do, step by step how to Jailbreak iOS 4.2 on iPhone 4, iPhone 3GS, iPhone 3G, iPad (on iOS 3.2.2) and iPod touch 4G / 3G / 2G using the newly released RedSn0w 0.9.6b2 jailbreak tool for Windows or Mac

Today Apple released to developers the GM seed for 4.2. Tinkerers will find that yesterday’s redsn0w jailbreaks today’s 4.2 GM seed, simply by pointing redsn0w at the 4.1 IPSW (rather than the 4.2 one).

Right now it mostly only makes sense for JB app developers to do that because many apps (including Cydia itself) need to be updated for 4.2. However, if all you want to do is enable afc2 (to use iFunBox or other file browsers), or to tweak settings like Battery % and Homescreen wallpapers, then go for it (if you have valid paid access to the GM seed).

Be sure to uncheck the Cydia box, though! Ultrasn0w unlockers should stay very far away from this!!

Early this morning the iPhone Dev-Team released the new version of RedSn0w for Mac and Windows that uses the Limera1n exploit to support more devices and adds the ability to restore custom firmware IPSW files.

So if you are feeling adventurous, you can give Redsn0w 0.9.6b2 a try on iOS 4.2 GM release. Here are the currently supported devices:

iPhone 4, Phone 3GS, iPhone 3G, iPad, iPod touch 4G / 3G / 2G

Follow the instructions posted below to jailbreak iOS 4.2 GM release with Redsn0w 0.9.6b2. NOTE: All iPhone unlockers MUST STAY AWAY from iOS 4.2 until new version of Ultrasn0w unlock is available.

How to Jailbreak Your iPhone, iPad or iPod Touch Using RedSn0w (Windows)

Step 1: Create a folder on your desktop called Jailbreak or Pwnage or what ever name you want to use for it so you can easily find it later. For this tutorial I will use the “Pwnage” name for my folder.

Step 2: Download RedSn0w and place it in the Jailbreak folder. You can download RedSn0w 0.9.6b2 from here: ● Windows (mirror) and ● Mac (NOTE: You can find all these links at the end of this tutorial / article as well)

Extract the redsn0w executable from the RedSn0w zip file into the same folder.

Download iOS 4.2 & iOS 4.1 (required for Redsn0w 0.9.6b2) for your version of iOS device. All the links for all supported devices are listed below so please pick your download carefully. Obviously, if you have an iPhone 4 then pick the iPhone 4 download file, and so on.

Select your iPhone from the list of devices on the left. Now hold down Shift and click the Restore button. Restore is preferred as it won’t create any wasted space on your iPhone.

Navigate to the Pwnage folder on your desktop and select the 4.1 firmware ipsw. Click the Choosebutton to continue.

Step 3: Once iTunes has finished updating your iPhone to the desired firmware open the Pwnage folder on your desktop and launch the redsn0w application from the redsn0w folder we extracted earlier. Start Redsn0w 0.9.6b2 and point it to iOS 4.1 to proceed with the jailbreak.

Step 4: Once RedSn0w opens click the Browse button.

Step 5: Select the 4.1 firmware IPSW we placed in the Pwnage folder on our desktop then click Open. NOTE: You will browse to the iOS 4.1 Final Version, NOT iOS 4.2 GM Version.

Step 6:Once the firmware has been verified click the Next button to continue.

Redsn0w will now go through some automated steps in patching the kernel and prepare your Jailbreak data

Step 7: Now select “Install Cydia” and click “Next”. Optionally (if available), you can also select any other option you like. In my example below I’m using redsn0w to Jailbreak my iPhone 3G so that’s why I have selected the “enable battery percentage” option.

Verbose boot displays detailed information on boot of your device and is generally only needed by developers and advanced users.

Make sure Cydia is selected. For this tutorial we will also select Custom boot logo and Custom recovery logo.

When you click to select each custom logo option a dialog window will appear asking you to select the image. Locate the image you would like to use then press the Open button.

RedSn0w has options to Enable multitasking, Enable homescreen wallpaper, and Enable battery percentage. If you do not need multitasking we would recommend deselecting it as it makes your iPhone 3G run very slow.

Click the Next button to continue

Step 8: Now make sure your device is both OFF and PLUGGED IN to the computer before you click “Next”.

At this stage you will be presented with a screen where you will have to quickly hold “Power” button and then while holding the “Power” button, you will now have to hold “Home” button too. Now after few seconds release “Power” button but keep holding “Home” button until installation begins.

Hold down the Home button and the Power button for ten (10) seconds.

Release the Power button and continue holding the Home button until RedSn0w detects the device.

Your iPhone, iPad or iPod Touch will now reboot.

Step 9: RedSn0w will then begin uploading the new RAM Disk and Kernel. Sit back and enjoy while redsn0w will do all the rest for you.

Step 10: Once this is complete you will be notified that RedSn0w is done. Click the Finish button. When your iPhone, iPad or iPod Touch finishes rebooting (5 minutes or so) it will be jailbroken on the latest iOS 4.2 firmware with Cydia on the SpringBoard.